Spark plug



AM M, 393@ SPARK PLUG Filed March lO, 1933 Patented Apr. 14, 1936 2,037,239

UNITED/ STATES PATENT OFFICE SPARK PLUG James W. Jean, Altadena, Calif.

Application March 10, 1933, Serial No. 660,256

4 Claims. (Cl. 123-169) My invention relates to improvements in To these ends my invention comprises the spark plugs characterized by the use of three features or construction and combination or readily separable assembled units, one an outer parts hereinafter described and claimed. shell which is secured through the Wall of the In the accompanying drawing forming part 5 combustion chamber of an internal combustion of this speciiication, Fig. 1 is a vertical section 5 engine and carrying or forming an outer elecof my invention on an enlarged scale, part of trode, second an insulator which is detachably the interior structure being shown in full side secured in said shell, said parts having a gas elevation and part of said structure being shown tight joint therebetween, and third a central or broken away and in section; Fig. 2 is a full side inner electrode which is held in juxtaposition elevation of my invention, approximating nor- 10 to the outer electrode and which is detachably mal or full size; Fig. 3 is a side elevation of the secured to said insulator by a gas tight joint, insulator separate from the remaining coopersaid parts being readily combined into a single ating parts; Fig. 4 is a full side elevation of the structure or separated and which are effectively inner electrode; Fig. 5 is a vertical central sec- 16 protected from short circuiting and from betion of the bushing, and Fig. 6 is a cross secl5 coming over heated when used. Among the adtion taken on line 6 6 of Fig. 1.

Vantages attained by my invention may be men- In the drawing A indicates the metallic shell tioned the following: of my improved spark plug which is externally 1st. A spark plug which will withstand exthreaded at I0 on its lower end to screw into 20 tremes of heat and cold without cracking, the usual threaded spark plug hole in the wall 20 breaking or leaking gas. 2nd. A substantially of the combustion chamber of an internal comunbreakable and indestructable spark plug bustion engine and which is externally shoulwhich has a maximum of efficiency, coupled with dered on its upper end at II for engagement long lasting qualities. 3rd. A spark plug that by a wrench to assist in screwing and tightening permits of quick and easy dismantling of parts the plug in the cylinder wall. Internally the 25 for quickly inspecting and cleaning and which shell is passaged longitudinally at I3, the upper assures quick and positive reassembly of parts portion being larger in diameter than the lower by skilled or unskilled labor in an effective manand internally threaded at I4 for engagement ner and with gas tight joints, without breaking. by the external threads I5 of a bushing B to be 4th. A spark plug that assures a clean spark hereinafter described. The upper and lower 30 plug and delivery of all of the current to the sections of the passage I3 are joined by a downspark plug at all times, thus resulting in a fat wardly and inwardly tapering shoulder I6 which spark as the current jumps across the spark forms an annular seat above which an external gap and assurance against a foul plug, and 5th. shoulder Il on the insulator element C is adapt- The complete suppression of leakage which ed to rest with a washer I8 therebetween. The 35 otherwise tends to cause static in radio sets used lower end of the shell is provided with the usual in motor vehicles. outer electrode terminal I9 which is directed in- A common source of trouble with spark plugs wardly in juxtaposition to the lower extremity results from a coat of carbon deposited on the of the inner electrical terminal D to be hereinsulator in the casing. This carbon deposit inafter described. In use the shell is screwed 40 thereby forms a. pathway for the current that is tightly into the spark plug opening of the inof much less electrical resistance than the gap ternal combustion engine with the spark gap in jump. Since electricity follows the line of least or adjacent to the combustion chamber so as to resistance, the current takes this path over the function in the usual manner.

carbon layer, diverting part or all of the current The insulating element C which is composed 45 away from the gap. This results in a weakened of porcelain or any other suitable insulating spark or no spark at all with consequent loss of material has a cylindrical body 20 formed with power, rapid accumulation of carbon and coma long gradually tapering lower end 2| having plete failure of the cooperating cylinder and said slightly curved annular shoulder I'I joinpiston. Another source of trouble with spark ing their surfaces. The upper portion of the in- 50 plugs results from leaking of water around the sulating element resembles a cylindrical stern plug or through the parts of the plug, this be- 22 of less diameter than and joined to said ing particularly true in cold and wet weather. cylindrical body 20 by a slightly curved upper These objections are entirely overcome by my seat 23. The cylindrical surface of the stem improvement. 22 is provided with a plurality of longitudinal 55 circumferentially spaced dead air channels 24 for absorbing heat from the metallic and porcelain parts of the spark plug. Internally the insulating element C is centrally passaged at 25 throughout its length to receive and hold the inner electrode D. In use the insulating element and shell are assembled with the annular shoulder Il resting above the seat l and with the washer i8 between to assist in producing a gas tight joint while the lower tapering end 2| projects downwardly in the main passage of the shell.

The portion of the insulator 2|, within the metallic shell A or firing chamber of the plug has a glazed outer surface which reduces tendency for carbon to collect thereon, and the portion 22 outside of the firing chamber, that is above said shell and within the insulating cap E has an unglazed outer surface which tends to retard conductivity of static producing electrical energy.

The bushing B is screwed down with its lower upwardly and inwardly tapering annular end 26 pressing downwardly against the annular seat 23 for holding the insulating element in leak tight rigid connection with the shell. This bushing has a cylindrical longitudinal passage 2'! above its lower end 2S, which flts freely over the stem 22 of the insulating element. The outer surface of the bushing below its upper ends is shouldered at 28 for engagement by a wrench to turn and tighten the bushing. The upper end of the bushing resembles a collar 29 for the purpose to be hereinafter described.

The inner electrode D resembles a rod which is thrust down through the passage 25 in the insulating element and which is formed with a downwardly tapering threaded head 30. This threaded head is adapted to screw into a downwardly tapering threaded socket 3| (See Fig. 1) in the upper end of the insulating element C to tightly secure the inner electrode therein. Above the threaded head 30 is a circular shoulder 32 and above said shoulder is an upwardly tapering threaded nipple 33 constituting an inner electrical circuit engaging terminal.

E is an insulating cap resembling a thin shell composed of composition resembling high iire test Bakelite or any other suitable electrical insulating and heat absorbing moisture proof material. This cap nts down snugly over the annular collar 29 on the bushing to produce a tight joint and has a central opening 34 in its upper end through which the inner electrode D including its head 3i! is thrust downwardly and screwed tightly home in the insulating element C, In this position the annular shoulder 32 clamps the insulating cap tightly down over the collar on the bushing and assists in sealing the upper end of the bushing B, insulating element C and inner electrode D from water or other liquid. In this manner the parts of the spark plug are thoroughly protected against leaking and short circuiting. A thin packing or jacket 35 of cork or other suitable heat absorbing and electrical insulating material is placed snugly over the stem 22 of the insulating element and within the insulating cap E and in conjunction with the channels 24 serves to absorb heat from within the spark plug and electrically insulate the parts, thus serving to reduce the hazard of the material constituting the insulating element C from cracking and rendering the upper end of the spark plug substantially cool at all times. Also the material 35 being comparatively soft acts as a buffer for protecting the fragible insulating element C from impact.

When desired a circuit terminal (not shown) of the internal combustion engine may be clamped on the collar 32 of the inner electrode by a cap screw 36 which is threaded over the nipple 33 of the inner electrode or the cap screw can be turned down securely over the threaded nipple 33 and a circuit terminal of usual construction engaged thereover in a circular channel 3l which is provided for that purpose.

In use the inner electrode assembly can be removed from the outer electrode shell while the shell is screwed in or removed from the engine by unscrewing the bushing B. The lower tapering surface 2i of the inner electrode insulator C can then be cleaned and the parts quickly reassembled. If it is desired to clean the inner electrode it can be done when dismantling the shell and insulating element or independently thereof by unscrewing and removing it from the insulating element and after cleaning replacing. While the inner electrode is removed the insulating cap E and heat absorbing element 35 can be removed or if the shell A and insulator C have been dismantled the bushing can be lifted off of the insulator and the parts inspected, wiped and reassembled quickly and effectively. Thus it is apparent my improved spark plug provides an inner electrode which can from time to time be easily end quickly examined, cleaned and replaced with or without disturbing any of the other parts of the spark plug or without removing the plug from the internal combustion engine. This is a distinct advantage and promotes the effectiveness of the device. Also the entire inner electrode assembly can be removed at any time without disturbing the outer electrode shell, which is an advantage,

In accordance with the patent statutes, I have described the principles of operation of my invention, together with the construction thereof which I now consider to represent the best embodiment thereof, but I desire to have it understood that the construction shown is only illustrative and that the invention can be carried out by other means and applied to uses other than those above set forth within the scope of the following claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

l. A spark plug, comprising, in combination, an outer electrode shell having an electrode. terminal on its lower end, an insulator in and having a stem projecting above said shell, said stem being channeled longitudinally on its` upper end to produce air pockets, fastening means for holding said insulator in said shell, a cap of insulating material placed over the upper end of said insulator and fastening means, a heat absorbing jacket between said cap and insulating stem whereby conductivity of heat from the stem is retarded, and an inner electrode rod removably thrust through said insulator and cap with its lower end in juxtaposition tol said outer electrode terminal and having means by which the upper end of said rod is detachably secured to said insulator and said cap is sealed over said insulating stem and fastening means.

2- A Spark plus', comprising. in combination, an outer electrode shell having an electrode terminal on its lower end, an linsulator in said shell, having an annular shoulder and a stem projecting above said shoulder and shell, said stem being passaged longitudinally, fastening means engaging said insulator above said shoulder and in threaded engagement with said shell, a moisture proof cap or low heat conductivity placed over said stem and fastening means and passaged longitudinaly, an inner electrode rod removably extending through the passage in said insulator and cap with its lower end in` juxtaposition to said outer electrode terminal and having a head piece screw threaded into said insulator to removably hold the inner electrode in said insulator and formed with an annular' shoulder adapted to removably engage and hold said cap over said stem and fastening means, and means occurring between the cap and the insulator for permitting a circulation of air therebetween.

3. A spark plug for internal combustion engines, comprising, a metallic shell adapted to be secured within the engine head, an electrode carried by said shell, an insulating member extending into the shell and secured thereto and sealed therein at a point intermediate its ends, and having a projecting stem channeled longitudinally, whereby a portion of the insulator will be within the ring chamber of the engine and the channeled portion will be outside the ring chamber, an electrode carried by the insulator, and a cap formed oi dielectric material and secured over the portion of said insulator outside the n'ng chamber, and means occurring between the cap and the stem of said insulator for permitting a circulation of air therebetween.

4. A spark plug for internal combustion engines, comprising, a metallic shell adapted to be secured Within the engine head, an electrode carried by said shell, an insulating member extending into the shell and secured thereto and sealed therein at a point intermediate its ends and having a projecting stem channeled outwardly Whereby a portion of the insulator will be Within the ring chamber of the engine and its stem Will be outside the ring chamber, an electrode carried by the insulator, a cap formed of dielectric: material and secured over the stem portion of said insulator outside the firing chamber, means occurring between the cap and the insulator for permitting a circulation of air therebetween, and heat insulating lining disposed between the cap and the insulator.

JAMES W. JEAN. 

